Clinical evidence in the USSR and abroad estimates the incidence of scoliotic disease in children of different ages to be from 4 to 6 percent on the average.
Scoliotic disease can be treated by conservative and surgical methods.
The now-existing conservative methods of treatment, such as therapeutic physical training, physiotherapy, correcting jackets prove to be efficacious not at all times, which necessitates searching for more perfect and reliable surgical methods of treatment. Thus, at least one child per every 1.5 thousand children needs surgical treatment. Therefore, many orthopedic specialists in leading countries of the world are now engaged in improving the now-existing surgical methods of treating scoliosis and kyphosis and in searching for new and more efficacious and economic ones.
Surgical treatment of scoliosis and kyphosis involves application of a great many diverse metallic structures and appliances for correcting the curvature of the spine and stabilizing the latter, which are implanted into the body of a patient either completely or partially.
Modern methods of surgical treatment applied for correcting spinal curvature, in particular, scoliosis incorporate as a rule two principal stages. At the first stage a fairly complicated and prolonged surgical intervention is carried out in order to rectify the spine, wherein the spine is mobilized by resecting the ribs and the transverse and spinous processes, dissecting the trunk erector muscles and both of the psoas muscles, whereupon the spine is rectified and fixed in that position with the aid of implantable correctants, straight rigid rods being most commonly used as such correctants and made fast on the bony structures of the spine. The second stage of the operation is in fact spondylosyndesis, that is, uniting of the vertebrae by virtue of osteoplasty.
Known in the present state of the art are some devices and appliances for stabilizing and correcting the spine by virtue of exertion developed thereby and applied lengthwise the spine, e.g., Harrington's distractor (cf. Harrington P. R. "Treatment of scoliosis. Correction and internal fixation by spine instrumentation". The Journal of Bone and Joint Surgery, vol. 44-A, No. 4, 1962, pp. 591-610).
The distractor comprises a straight rigid metallic rod provided with a hook at each end for the rod to fix on the spine. One of the rod ends has a thread in the form of cones for the hook to lock in a desired position.
A surgical operation for implanting the aforesaid rod occurs as follows. An incision is made lengthwise the spine to expose spinal bony formations, i.e., spinous and transverse processes, vertebral arches on both sides of the spine, viz, the convex and concave ones. Then holes are made between the arches of adjacent neutral unaffected vertebrae of the thoracic and lumbar spine to receive a respective hook, whereupon the rod and hooks are so positioned that the rod end provided with cones be situated in the superior portion of the trunk.
The rod is positioned on the concave side of the spine and fixed in place, using the hooks, by the arches or transverse processes of the vertebrae above and below the vertex of a spinal curvature. Next while moving the top hook along the rod one must distract the spine lengthwise, thus eliminating its curvature, whereupon the hook is locked in position.
Once the spine has been rectified bone grafts are placed on both sides of the vertebral spinous processes for the purpose of spondylosyndesis, where the operative wound is stitched up using layer-by-layer technique. The process of spondylosyndesis occurs within subsequent 3 to 5 months.
However, such exertion directed lengthwise the spine results in that high forces must be applied for rectifying a spinal curvature which migh cause fracture of the vertebral bony structures at the places of fixation, traction of the spinal cord, deranged function of the pelvic organs, paresis and paralysis of the lower extremities.
Thus, complete rectification of the spine cannot be obtained by the afore-discussed method.
In order to attain a higher degree of straightening of the spine and at the same time to render destruction of the spinal bony formations less probable, provision is made for some methods of treating a curvature of the spine with the help of a correctant with a transverse brace (cf. Cotrel "Techniques nouvelles dans le traitement de la scoliose idiopathique". International Ortopedics, vol. 1, No. 4, 1978, pp. 247-265).
The aforesaid correctant comprises the Harrington's rod discussed above, which is set on one side of the spinous processes at the spine concavity, and an additional transverse brace made as a short plate with hooks for the transverse processes to catch, said plate being positioned at the vertex of the spinal curvature on the other side of the spinous processes and being drawn to the rod by virtue of a threaded joint.
However, the afore-discussed constructions of implantable correctants of the spinal curvature based on the principle of exertion applied lengthwise the spine, can be used only in children whose growth has been completed, whereas use of such constructions in children with uncompleted growth is unreasonable, inasmuch as the spine of the children elongates with their growth, and the correctants lose the correcting effect within a short period of time.
In addition, insofar as both the convex and the concave sides of the spine are subjected to distraction in the course of the spinal curvature rectifying, such a construction of implantable correctant fails to provide proper conditions for a more intense growth of osseous tissues on the concave side of the spine in order to stabilize the position of the spine attained during the curvature straightening process, by equalizing the size of the vertebral bony structures on the convex and concave sides of the spine.
Prior-art implantable correctants of a spinal curvature are known to provide for correction and stabilization of the spine by exertion applied thereto square relative to its longitudinal axis (cf., e.g., the journal "Orthopedics, Traumatology and Prosthetics", No. 4, 1969, pp. 22-32/in Russian/). These constructions are in fact straight rigid metallic plates having a number of holes to receive a plurality of hooks having threaded ends. The hooks are adapted to catch the arches or the vertebral transverse processes situated at the vertex of the spinal curvature on the side opposite to that of the plate, which is situated on the concave side of the spine. Then the threaded ends of the hooks are passed through the respective holes in the plate or engaged with the plate, and the nuts are drawn until the spine is brought up close to the plate. As a result, the plate, the spine and the hooks define a rigid structure.
However, the afore-mentioned constructional arrangement of implantable correctants of a spinal curvature as a straight rigid rod or plate fails to provide an adequate correcting effect on the spine within the postoperative treatment. Oftentimes a repeated operation has to be performed to restore a requires amount of correcting action, and additional pulling up of the spine with the hooks by drawing up the nuts.
One more implantable correctant of a spinal curvature (cf. I. Resina and A. Ferreira Alvez, "A technique of correction and internal fixation for scoliosis". The Journal of Bone and Joint Surgery, vol. 59-B, No. 2, May, 1977, pp. 159-165) is known to be an elastic metallic rod fitted on the convex side of the spine and fixed with a wire at several points along the length thereof to the bases of the spinous processes, wherein holes have been made beforehand. Thus, the spine is rectified by virtue of elastic forces developed by the rod.
However, such an elastic rod fails to perform hypercorrection of the spine, i.e., to deflect the line of arrangement of the spinous processes in the direction opposite to the initial spinal curvature in order to eliminate torsion of the vertebrae and provide more favourable conditions for equalizing the size of the vertebral bony structures on the convex and concave sides of the spine by retarding and promoting the growth of osseous tissue, respectively.
Fixation pieces of all the afore-mentioned implantable correctants of a spinal curvature are causative of bone atrophy at the spots of bone-to-metal contact. That is why these correctants cannot be applied as permanent internal fixation pieces for correction and stabilization of the spine and have to be withdrawn in a comparatively short lapse of time long before completion of the treatment process, which in turn necessitates osteoplastic fixation of the spine, viz, uniting of the vertebrae by vertue of osteoplasty (spondylosyndesis). However, the osteoplastic fixation fails to maintain the extent of correction attained.
In order to intensify the rectifying action of implantable metallic appliances and devices and reduce the loss of the amount of correction attained, surgeons are to preliminarily mobilize the spine by performing complicated surgery on soft tissues, the spine and the thoracic cavity, e.g., severing the long dorsal muscles; dissecting the trunk erector muscles and the psoas muscle; resection of the vertebral and costal bodies; resection of the spinous, transverse and articular processes of the vertebrae; dissecting the fibrous rings of the intervertebral disks at several levels followed by enucleation of said disks.
However, such complicated surgical interventions prove to be vitally dangerous due to their being causative of shocks and involving large loss of blood.
Moreover, such a method of treatment is inadequately efficient, i.e., the correction attained due to the surgery carried out is lost by about 30 to 45 percent soon after the operation, whereby repeated operations are necessitated.
Still one more implantable correctant of a spinal curvature (cf. USSR Inventor's Certificate No. 450,572 issued on Dec. 15, 1974, published on Nov. 25, 1974 in Bulletin No. 43) is known to have an arcuate shape and be positioned with its convex side towards the convexity of the spine lengthwise the spinous processes and made fast on the spine by means of a fixation device so that the correctant gets partially straightened to build up a force for the spine to rectify. The correctant comprises a plurality of arcuate plates, four or five such plates being placed on each side of the spinous processes so that the plates situated on one side of said processes are in a close contact with one another to form a spring. The spine fixation device is made as a number of wire coils with which the plates and the spine are brought together, said wire coils catching the vertebrae by their arches.
However, such a constructional arrangement of the implantable correctant of a spinal curvature requires that an operative procedure for implanting said correctant should involve extensive bilateral stripping of the spine from the surrounding muscles.
Securing the correctant plates to the vertebrae with wire coils is a fairly labour- and time-consuming part of the surgery involved.
This may inflict an extensive traumatic intervention resulting in large blood loss (1200 to 2000 ml per operation) and in a prolonged operating time (2 to 3 hours), whereby such operations become vitally dangerous. It should also be noted that bilateral exposure of the spine inflicts trauma upon those groups of muscles which must be retained intact for patient's rehabilitation by auxiliary therapy methods, e.g., by exercise therapy or physiotherapy. In addition, bilateral exposure of the spine causes more frequent complications on the part of the operative wound, such as suppuration, seromas and even paraplegia.
On completing the course of treatment the correctant must be withdrawn, for which purpose repeated operative procedures should be resorted to.
Besides, mutual slipping of the correctant plates and their rubbing against one another are often causative of metalosis accompanied by formation of sterile seromas.
High extent of traumatic lesion resulting from an operative procedure for fixing the correcting rod to the spine creates a psychological barrier to practical application of the method. At early stage of the spine curvature in a child it is difficult to persuade his/her parents to subject the child to such an extensive operative intervention. This leads to the situation in which, surgical treatment is resorted to only in an inextricable situation in the case of a grave form of the spinal curvature, that is, the due time of treatment when it is much more efficacious, is missed. To fix the implantable correctants to the vertebral bony structures with a plurality of wire fasteners is a labour-consuming procedure taking much time to carry out. To control the degree of twisting of the wire fasteners of the correcting rods proves to be practically impossible.
When overtwisted (to provide a stronger fixation) the wire is liable to break or destructs the vertebral bony structures, whereas undertwisting of the wire fasteners results in loosened rod-to-spine attachment. As a result, there might occur within the postoperative period some displacement of the rod relative to the spine, whereby the correction attained earlier becomes lost. This, in turn, necessitates a many-month (18 to 24) postoperative treatment course with the help of plaster-of-Paris and removable jackets, which restrains patients' active motility and imposes limitation upon application of means and measures of exercise therapy to attain rapid rehabilitation; hence, the use of wire for fixation of the spinal curvature correctant fails to develop forces high enough for a complete spine rectification.
Thus, an operative procedure for implanting the aforesaid correctant is a very complicated one due to its being causative of shocks and a large amount of blood loss and take much time to occur, which tells adversely on the results of treatment.